1. Field of the Invention
The present invention relates to an image forming apparatus to which the known electrographic method or magnetic recording method is applied, for example, a copying machine or a recording or printing apparatus. The present invention relates to also a detachable unit for use in such image forming apparatus.
2. Description of the Prior Art
Hereinafter, the conception of the present invention will be described with reference to an electrophotographic copying machine as an example of the image forming apparatus pertinent to the present invention.
In an electrophotographic copying machine, the photosensitive medium deteriorates with time or is occasionally damaged. Therefore, it requires replacing the used photosensitive medium with a new one. After exchange of the photosensitive medium, however, sometimes the tone of image of the copy made by the new photosensitive medium is different from that of the copy made by the old one. This is caused by differences in sensitivity, charging characteristic, residual potential characteristic etc. These differences are attributable, for instance, to the date of manufacture of the two photosensitive mediums. If they were manufactured on different days, it is quite possible that the mixture ratio of materials for forming the photoconductive layer and/or the physical and chemical treatment conditions for forming the same employed for the new photosensitive medium were slightly different from those employed for the old one. In such case, it is no longer possible to obtain a good image by the new photosensitive medium under the same conditions of amount of corona charge, amount of original exposure etc. as previously set for the old one as optimum.
Therefore, until now it was required to read just the previously set image forming conditions such as the amount of charge and the amount of exposure at the time of photosensitive medium exchange. However, such adjustment of the image forming conditions generally requires a special knowledge about it and an unskilled user can hardly set the necessary image forming conditions. This applies also to such case where the photosensitive medium is contained in a unit which can be mounted on and demounted from the main apparatus aiming at the simplification of exchange.
As a development of the idea of a detachable unit for an image forming apparatus, there is a thought that the main apparatus may be used for many different purposes making full use of the common part. However, if an exchange of such unit is done only with the intention of using different types of developing devices of the two units for different purposes, it will produce only a limited effect for use in multiple-application. Furthermore, the advantage of using such unit is minimal if process change and other adjustments are required each time a unit is mounted on the main apparatus.